JP-A 1991-27150 and JP-A 1992-289242 disclose the ratio of consumption between a ground warp and a pile warp, namely, disclose that a pile scale factor is compared with a target value, and a swinging torque of a tension roll of the pile warp is adjusted in a direction to cancel the amount of deviation relative to the target value, thereby changing the pile warp tension or adjusting a reed escape amount (appropriate distance between the position of the cloth fell caused by the movement of a cloth and the original position of the cloth fell, i.e. beating position of the cloth fell).
Further, JP-A 1988-264946 discloses a pile loom for rotatably driving a ground warp beam at a speed corresponding to a weaving speed (taking-up speed) wherein the number of revolutions of the pile warp beam is controlled such that the rotation of the pile warp beam is controlled in a direction to keep the deviation of the warp tension, and the ratio of consumption between the ground warp and the pile warp, namely, the pile scale factor.
Any of the foregoing techniques functions to keep the pile scale factor, in other words, the consumption of the pile warp, at a target value. However, in any of the techniques, the weaving condition such as pile warp tension is frequently adjusted in a direction to allow the pile scale factor to approach the target value, which causes problems in that the operation of the loom is unstable and the quality of the pile fabric is deteriorated.